Various types of analytical tests related to patient diagnosis and therapy can be performed by analysis of a liquid sample taken from a patient's infections, bodily fluids or abscesses. These assays are typically conducted with automated clinical analyzers onto which liquid patient samples have been loaded. The analyzer extracts liquid sample from a container and combines the sample with various reagents in special reaction cuvettes. Usually the sample-reagent solution is incubated or otherwise processed before being analyzed. Analytical measurements are performed using a beam of interrogating radiation interacting with the sample-reagent combination to generate absorption readings or the like. The readings allow determination of end-point or rate values from which an amount of analyte related to the health of the patient may be determined using well-known calibration techniques.
Within such analyzers, a large number of liquid sample and reagent aspiration/dispensing probes are usually employed in order to extract incoming sample from a container, dispense aliquot portions of said sample into an aliquot array, to aspirate aliquot samples from the array and dispense aliquot samples into a reaction cuvette, and/or to extract reaction reagents from a container and directly dispense aspirated reagents into a reaction cuvette. In addition, within such analyzers, a very large number of electrical cables are interconnected between the various electromechanical controlling and controlled devices. For space-saving reasons, a popular electrical cable is shaped like a flat ribbon and is formed of a number of electrical conductors covered by an insulator and placed side-by-side. Ribbon electrical cables are frequently utilized to direct electrical signals between stationary printed circuit boards and electromechanical devices that are translated horizontally and vertically for millions of cycles. In a typical static application a latch may be sufficient to retain the cable securely. However, in applications in which substantial and/or sustained movement is encountered like described, latches are usually found to be inadequate over periods of sustained use. Thus, a need exists for a retaining device which secures the cable firmly irrespective of substantial sustained movement.
In order to minimize impact upon patients as well as to decrease the costs of clinical assays, the volumes of liquid sample aliquots and reagents are increasingly made smaller, in the range of about 1 microliter to five microliters; therefore, the pumping systems associated with sample and reagent aspiration and dispensing probes must be capable of handling precise precisely known and controlled liquid volumes. Almost all sample and reagent aspiration/dispensing probes are mounted on translatable arms having both horizontal and vertical motion in order to translate probes between locations as well as to raise and lower probes into and out of containers. Consequently, a popular practice is to attach a probe to a pumping system using flexible tubing within a guide chain; furthermore, to reduce pumping volume uncertainties, the tubing is filled with an inert liquid, as opposed to air, between the pumping system and the probe. The tube is also generally secured on and between stationary and/or moving parts using a guide with circular dimensions. To run such tubes, in particular from a stationary junction point to a movable device like a dispensing probe, it is common to use so-called line guide elements which are interconnected to form an energy conducting guide chain, like those available from Igus GMBH (KoIn, Germany).
For example, U.S. Pat. No. 6,745,555 discloses an energy guiding chain, in which the articulated joints include joint elements that are elastically deformable in the bending direction of the chain links and designed as separate components, where the joint elements extend partially between the inside and outside lateral surfaces of the straps.
U.S. Pat. No. 6,550,233 discloses an energy guiding chain having a plurality of plastic chain links that are connected to one another, each of which includes two side straps and two cross-members, where the cross-members are connected to the side straps in detachable fashion. A snap mechanism is provided which interacts with a snap ridge provided on each end of the cross-members.
U.S. Pat. No. 6,170,249 discloses an energy guiding chain for accommodating cables and hoses. The chain has laterally spaced parallel side-plates with upper and lower cross-members. A cross-sectional space for cables and hoses is defined by the side-plates and the upper and lower edges of the side-plates. The cross-sectional space is expanded since at least one of the cross-members is detachably mounted on the side-plates.
U.S. Pat. No. 5,980,409 discloses an energy transmission chain with high lateral stability, particularly when installed in a lateral position.
While these energy guiding chains are quite useful in handling cables and hoses, it t has been discovered, however, that the tubing must be precisely placed and maintained along the central radius of curvature of such a guide in order to prevent a “peristaltic-type” pumping action of the fluid within the tube as the curved section of tubing moves. If the tubing falls to the inside of the guide, the tubing is slightly compressed; likewise, if the tubing falls to the outside of the guide, the tubing is slightly stretched. Both actions cause a change of volume of fluid inside the curved portion and a pumping action is created as the probe is translated between aspirate and dispense locations and the tubing is moved in opposite directions along a circular guide. This false pumping is in addition to the controlled pumping, thereby adversely affecting the accuracy of the aspirated or dispensed sample/reagent liquid.